It is well known that nucleic acids, including, for instance, double stranded ribose nucleic acid, have been employed as interferon inducers, cytotoxic agents or for the purpose of gene-transfer. However, one attendant disadvantage is that such nucleic acids exhibit little if any cell-type specificity. It has now been found that this disadvantage can be overcome by linking or attaching the nucleic acid to a protein whereby the cell-type target is chosen by the protein molecule. After binding to the cell surface, the nucleic acid can then interact with its cell-surface receptor, or if the protein is internalized by receptor-mediated endocytosis, the nucleic acid can interact with one of the intracellular nucleic acid-dependent enzymes and assert its action. In addition, through protein-nucleic acid linkage, the uptake of nucleic acid can be accompanied by an enzyme to increase the biological effectiveness of the nucelic acid-enzyme conjugate.